1. Field of the Invention
The present invention relates to a home-position detecting method for detecting a home position of an operation target member, a sheet processing device that carries a sheet-like recording medium (simply referred to as “paper” in the present specification), and performs the home-position detecting method of a processing unit that performs a predetermined process, and an image forming apparatus including the sheet processing device.
2. Description of the Related Art
A sheet processing device having a function of feeding paper and performing a predetermined process on paper essentially requires a so-called homing operation of a home-position return operation to control positions of various mechanisms that perform paper punching, paper alignment, stapling, or the like. The homing operation is performed by combining a prescribed pattern operation with detection information of a position sensor. The homing operation also includes an abnormality detection operation, and the sheet processing device determines that the mechanism is abnormal when the homing operation cannot be normally performed. The homing operation is performed mainly at the time of turning on a power source or when a door of the device is closed.
As a technique related to the homing operation of the sheet processing device, inventions described in Japanese Patent Application Laid-open No. H11-334983 and Japanese. Patent No. 3635898 are known. Japanese Patent Application Laid-open No. H11-334983 discloses a sheet post-processing device capable of detecting, in a simple configuration, a deviation of a binding position of sheets of paper at the time of performing a binding process to the sheets. To increase the reliability of the binding process, the sheet post-processing device includes: a processing unit that processes sheets; a processing-unit moving unit that moves the processing unit to a sheet processing position by driving a pulse motor; a pulse generating unit that transmits a pulse to a pulse motor that drives the processing-unit moving unit; and a home-position detecting unit that confirms a completion of the operation of the processing-unit moving unit. When the processing-unit moving unit moves, the sheet post-processing device compares the generated number of pulses scheduled in advance with the number of pulses generated by the pulse generating unit, when the home-position detecting unit detects the home position. With this arrangement, the sheet post-processing device detects an abnormal operation of the processing-unit moving unit.
Further, Japanese Patent No. 3635898 discloses an image forming system including an image forming apparatus, and a paper post-processing device that performs post processing of paper discharged from the image forming apparatus. The image forming system includes a control unit that controls the paper post-processing device to prohibit all operations of the paper post-processing device other than communication, during an energy saving mode in which power is supplied to the paper post-processing device and the paper post-processing device can communicate with the image forming apparatus. When a body door of the paper post-processing device is opened or closed during the energy saving mode, the energy saving mode is shifted to a normal mode, and the control unit controls the paper post-processing device to perform an initial operation.
As described above, in operating the homing operation, various kinds of mechanisms are driven to move members to be position-controlled or stopped. Therefore, noise occurs, power is consumed, and parts are abraded due to this operation. Particularly, a recent multi function peripheral such as the paper post-processing device (for example, a finisher) includes many mechanisms that perform homing operations. Therefore, the multi function peripheral requires a long time to complete the homing operation of the mechanism, and delays the processing operation, in addition to having the above inconvenience.